(524b) Combating Pseudomonas Aeruginosa Biofilm Infections Using Synergistic Drug Therapies

Bacterial biofilms are formed when planktonic bacteria attach to a surface and create a polysaccharide matrix for protection.  Within the body, bacteria in biofilms are less susceptible to antibiotic therapy and the immune system, causing current antibiotic treatments to be ineffective.  Combinations of antibiotic drug compound have also been unable to eradicate biofilms.  A new approach has focused on the use of dispersion compounds to entice the bacteria out of the biofilm, potentially enabling traditional antibiotics to kill the population of free-swimming bacteria.  Therefore, a combination therapy of both antibiotics and dispersion compounds may provide a synergistic effect in breaking up and eradicating biofilms.  It is our goal to develop dry powder aerosols to co-deliver dispersion and antibiotic compounds against pulmonary Pseudomonas aeruginosa biofilms.  This bacterium causes chronic lung infections in various patient populations, including patients with cystic fibrosis, patients on mechanical ventilation, and immunocompromised patients.

Dry powders were formulated via spray drying to contain antibiotic, dispersion compound, and L-leucine to improve the flow properties of the powders.  Key formulation and process parameters were varied to optimize the physical properties of the spray dried powders, including solids concentration in the initial solution, solution pH, liquid flow rate, atomizer air flow rate, and spray dryer inlet temperature. Optimized dry powder aerosols were formulated with up to 90% drug and had aerodynamic properties appropriate for deposition across the tracheobronchial and alveolar regions (mass median aerodynamic diameter = 3.0 – 5.3 µm).  

Screening studies were conducted to evaluate the ability of a single dose co-treatment of antibiotic and dispersion compounds to eradicate in vitro cultures of a biofilm-forming mucoid strain of Pseudomonas aeruginosa (BAA-47; ATCC).  Biofilms were exposed to various combinations of 6 antibiotic and 6 dispersion compounds. Twenty four hours after treatment, biofilms were stained with BacLight Live/Dead syto9 and propidium iodide stains, visualized via confocal microscopy, and quantified using COMSTAT.  Dispersion compounds tested individually resulted in biofilms growth or no statistical change in growth.  Synergy was found with four antibiotics and various dispersion compounds in reducing the total percent live bacteria remaining after treatment.  Overall, results from these studies suggest that fine-tuning of antibiotic and dispersion compound concentrations may allow lower doses of antibiotic to be delivered to eradicate the biofilms.